stfu Share definition Flag 1) The messaging acronym for "Shut the fuck up." 2) The initials of the fictional organization "Scarf Team Freaks United" Guy 1: OMGZ!!1!!eleven!!!! can i joinz teh stfu?!!?1?!?!?!!? Guy 2: Stfu, n00b. stfu by Zizefia September 6, 2007